The purpose of this study is to investigate the spatial distribution of brain lactate in children with lactic acidosis using 1H spectroscopic imaging. Brain lactic acidosis may occur in a number of very different conditions. Inborn errors of metabolism affecting the lactate-pyruvate metabolism or those leading to secondary lactic acid accumulation represent some of them. Data are acquired using either a hybrid of 1D, 4th order, transverse Hadamard Spectroscopic Imaging (HSI) and a 2D Chemical Shift Imaging (CSI) or a 2D CSI. With the hybrid technique multiple slices can be obtained, covering a greater volume of the brain. The volume of interest usually is 7x7x4 cm3. We apply this technique into the clinical setting. The patient population consists of children with the diagnosis of an inborn error of for instance the lactate metabolism, mitochondrial encephalopathies, primary lactic acidosis of unknown etiology. Data obtained in several patient studies revealed regional differences of brain lactate accumulation. The pattern of spatial distribution of lactate may identify different subsets of mitochondria which can be affected separately by different metabolic diseases.